In my passport, my birthdate is listed as "5 July." And yet, I am already celebrating my birthday. Yes, it is the 4th of July right now, so why can I justify it? Just because I want to cash in on the Independence Day celebrations in the US? No, not really (although it does play a little into it -- see below). The main reason why I can justify it is because I was born on Guam on 5 July. And when it was the 5th of July on Guam, it was still the 4th of July in the continental United States. So... since I was born on Guam, and I am now living in the continental United States, I can say (rightly) that it is already my birthday when the calendar reads "July 4" in Michigan.
But, why do it? Well, for a few reasons. True, I don't know of other people who do what I do, but I have decided to do it because July 4th is a major holiday in the United States, with barbeque parties, fireworks, very little traffic (in Ann Arbor), and generally good spirits. In comparison, July 5th is usually a difficult time to hold a gathering. If July 4th is on a Thursday, then people take a long weekend, and are away for my birthday. If July 4th is on a Friday, people are already away on my birthday (likely having left the city on July 3rd) -- and something similar happens if it were on a Saturday. If Independence Day is on a Sunday (like this year), many people take off the following Monday (my birthday). Only when Independence Day is on a Monday, Tuesday, or Wednesday is there a chance that people will be in town on my birthday on July 5th. However, no one wants to party, because they have spent too much time, money, and stomach space the day before to really want to celebrate.
... so I just celebrate my birthday based on Guam time. And it's been my birthday (on Guam) for several hours already. And now I'm off to a barbeque, quietly celebrating my birthday, like I do most years. I actually didn't grow up with large birthday parties, since most people (or, indeed, my own family) were away for summer vacation while I was growing up, meaning that my memories of most of my birthdays were with only my immediate family. Therefore, being happy in the company of friends while celebrating the birthday of the United States, while vicariously celebrating my own is actually quite nice, thankyouverymuch.
(Happy birthday to me... Happy birthday to me...)